Process and apparatus for the catalytic cracking of hydrocarbons



March 19, 1963 PROCE H. KROEPER ETAL 3,082,165 SS AND A RATUS FOR THE CATALYTIC RBO CRACKI OF HYDROCA NS Filed Feb. 16. 1959 3 Sheets-Sheet 1 FIG.I

INVENTORS: HUGO KRO R ROLF PLAT BY W M ATT'YS March 19, 1963 H. KROEPER ETAL 3,082,165

PROCESS AND APPARATUS FOR THE CATALYTIC CRACKING OF HYDROCARBONS Filed Feb. 16, 1959 5 Sheets-Sheet 2 l'la , mvrwrons: HUGO KROEPER ROLF} PLATZ ATT Y S March 19, 1963 H. KROEPER ETAL 3,082,165

PROCESS AND APPARATUS FOR THE CATALYTIC CRACKING OF HYDROCARBONS Filed Feb. 16, 1959 a Sheets-Sheet s F|G.4a

T- so 80 f 7 1 no FIG. 4a

IOO

INVENTORS HUGO' KROEPER ROLF PLATZ GYM 7 M AW United States Patent "ice This invention relates to a process and apparatus for the production of hydrocarbons by catalytic-cracking and especially to a continuous cracking process in which a fluidized layer catalyst is continuously regenerated.

Reactions with hydrocarbons which proceed purely thermally or catalytically are almost always attended by carbon deposits, sometimes very considerable, which make necessary a continuous or periodic regeneration of the heat carrier or catalyst.

It is already known to carry out this regeneration by simultaneous supply of steam and the reaction mixture to be reacted provided the chemistry of the reaction or the properties of the catalyst permit such a method of operation. in order that the wa'tergas reaction with the consumption of the carbon should proceed with sutficient speed, however, relatively high temperatures are necessary. Moreover the watergas reaction extracts heat from the system.

According to another known proposal, a discontinuous operation is used, for example as in cracking or especially in the dehydrogenation of butane according to Houdry, by removing the carbon deposited on the catalyst after a certain reaction period by burning it olf in a current of air or oxygen after the reaction chamberhas previouslybeen rinsed through with an inert gas. The combustion heat thereby occurring is accumulated in the catalyst or in heat carriers mixed with the catalyst. The accumulated heat superheats the catalyst above the temperature neces sary for carrying out the process and thereby serves to cover the heat requirement of the endothermic process. Operation in this way, however, makes a very accurate temperature regulation necessary because the catalyst may only be superheated to a certain extent. Since the reaction periods until interruption for regeneration of the catalyst amountto only a few minutes, complicatedreversing mechanism is necessary for carrying out the reaction and the regeneration and the intermediate rinsing of the reaction chamber.

Another method which is already known is that of continuously withdrawing from the reaction chamber the catalyst or heat carrier laden with carbon, regenerating it outside the reaction chamber and then returning it to the reaction chamber. This method which has been applied for example in catalytic cracking processes for the recovery of fuels has the disadvantage that it requires complicated apparatus and supervision means especially when this method is to be used in processes which proceed under reduced pressure.

Finally it has also already been proposed to lead the hydrocarbon to be reacted, together with oxygen, through afluidized layer of catalyst particles or heat carriers. In this process also it is necessary to regenerate the catalyst at short intervals of time because the oxygen preferentially burns the hydrocarbon and not the carbon separated on the catalyst or heat carrier. This disadvantage is therefore also accompanied by a diminution in the yield.

We have now found that the said disadvantages in processes of cracking hydrocarbons which take place with the fracture of C=H or C-C linkages can be avoided by carrying out the cracking in a fluidized layer of catalyst into which the hydrocarbon to be cracked, if desired to gether with one or more carrier gases, is led from below,

3,082,165 Patented Mar. 19, 1963 and another layer of fluidized catalyst, into which oxygenccntaining gas is led from below for the purpose of regeneration, is so arranged that the layer serving for the regeneration is in communication only at its upper end with the layer serving for cracking and, when these layers are arranged side by side, ends at such a distanc below the level of the layer for the cracking that a sufli cient exchange takes place between the regenerated cata lyst particles leaving the regeneration layer at the top an( the catalyst particles in the layer serving for cracking, ant so that the oxygen content and speed of the gas or gase: introduced into the regeneration layer are so regulatet that when the gas leaves this layer the oxygen is practical ly used up.

By working in this way, the heat set free in the regen eration of the catalyst can be made directly utilizable to. the cracking which proceeds endothermically.

The two fluidized layers may be arranged in a singlt reaction vesselfor example by arranging the layer servin; for the regeneration of the catalyst concentrically withiJ the annular layer surrounding the same and serving fo the cracking of the hydrocarbons. Such an arrangemen ensures a uniform loss of heat from the catalyst particle leaving the regeneration layer to the layer serving fo the cracking.

FIGURE 1 of the accompanying drawings shows sucl an arrangement diagrammatically. A reaction vessel 1 i provided with a grate or perforated base plate 2 abov which are situated fluidized layers 4 and 5 separated b a concentric tube 3. The hydrocarbons to be cracke are supplied to the fluidized layer 4 through a pipe t and oxygen-containing gas is supplied to the fluidized laye 5 through a pipe 7. The gaseous reaction mixture is 16 away through a pipe 8.

The height of the fluidized layer serving for crack-in for a given base area is determined by the upper limf of the permissible carbon loading of the catalyst. Th less the tolerable loading of the catalyst with carbo deposits in the cracking in any given case, the highe must be the layer serving for regeneration of the catalys This relationship may however alsobe taken care of b appropriate dimensioning of the base areas of the W fluidized layers.

Where the base area of the reaction vessel is largt the layer serving for the regeneration of the catalyst ma ing drawings which are sectionalplans and in which thes annular chambers are represented by hatching wherea the areas which are not hatched constitute the space serving for the cracking. The layer serving for regenerz tion may also be contained in a plurality of cylindricz chambers distributed over the cross-section, as indicate in FIGURE 20 of the accompanying drawings in whic three such chambers are shown.

An arrangement in which the layer serving for crackin and the layer serving for regeneration are arranged on above the other'is shown diagrammatically in FIGURE of the accompanying drawings. In a reaction vessel :It tapered conically at the bottom, there is arranged, abov a wind chamber 12, a perforated base plate 13' throug which is supplied oxygen-containing gas which is supplie from a pipe 14, which passes into a layer 17a of cataly particles situated above the base plate 13 and sets the pa ticles in fluidized motion. The hydrocarbon to be cracke is supplied through a pipe 15 and through a distributi plate 16 to the catalyst layer 17b situated above the sam The catalyst layers 17aand 17b communicate direct] with each other only through the annular space betwee the distributor plate 16 and the inner wall of the reactic vessel 11. The distance between the distributor plate and the base plate 13 can be regulated so that the oxyge supplied through the base plate 13 is used up by burning oil the carbon situated on the catalyst before it reaches the upper distributor plate 16. The fraction of the catalyst particles entrained from the layer 17b by the reaction gases is precipitated in a dust separator 18 and returned through a pipe 19 to the layer. The reaction gaS leaves the apparatus through a pipe 20.

The simplicity of the arrangement makes it possible to tion heat necessary for the dehydrogenation of the butylene is provided by combustion of a part of the initial product and the carbon formed during the reaction.

The reaction is interrupted from time to time in order to determine the amount of carbon deposited on the catalyst. The compositions in percent by volume of the reaction product obtained after various periods of time are given in Table I.

TABLE I [Composition of the reaction product in percent by volume] After hours Hi Methane Ethane CO CO; Butane Butylcne Butadiene Propane ethylene propylene 1 This value includes the content: of methane, ethane, ethylene, propane and propylene.

:arry out the process according to this invention at atmospheric, increased or reduced pressure.

The following examples will further illustnate this invention but the invention is not restricted to these examples. The percentages specified are percentages by weight. 25

From this table, by converting the percent by volume to percent by Weight and deducting the oxygen of the oxides of carbon, the values given in Table II are obtained.

TABLE II Calculated as C Buta- Etliane diene Propane Yield of Alter hours 11; Methane ethylene Butane Butylene degree of propylbutadi- C 0 CO: eonverone one sion 12 1. 23 1. 3 1. 6 1.7 2. 45 1. 35 63.5 24.0 2. G5 81 50-- 1. 30 1. 1. 5 1. 45 2. 1.0 64. 3 23.5 2. 81. 4 1.17 1. 40 1. 2 0. 06 1. 95 1. 2 64. 2 22. 7 4.17 76.0 1. 20 1.46 0.7 1.61 1.33 1.32 64. G 24. 5 3.07 86.0 443 1. 68 1. 65 2.17 1. 7 63. 2 24. 9 86. (J

Example 1 (a) The reactor consists of a vertical tube having a diameter of 60 mm. and a height of 300 mm. and closed at the bottom by a sieve plate. Through the sieve plate there projects into the interior of the tube another tube having a diameter of 40 mm. and a height of mm., so that the two tubes enclose between them an annular space of 8 mm. in width. The two tubes are provided beneath the sieve plate with separate gas supplies. The reactor is heatinsulated and is provided with electric heating by which the heat necessary for the initiation of the reaction can be supplied. Measurement of temperature takes place by thermoelements.

The reactor is filled to a layer height of to mm. with pulverulent catalyst (aluminum oxide with 12% of chromium oxide) of a grain size of 0.1 to 0.3 mm. so that the upper edge of the inner tube is covered to the extent of about 10 mm. by the layer. While simultaneously heating by means of the electric heating means, the catalyst is set in fluidized motion by a current of nitrogen until the temperature necessary for the reaction has been set up in the reactor. Then, instead of nitrogen, there is led through the annular space oxygen in an amount of 5 liters per hour, and at the same time, through the inner tube, 30 liters per hour of butylene with a content of 0.5% of butane and 5.8% of C and C hydrocarbons while maintaining a pressure of 50 to 60 mm. in the reactor. The gas speeds of the butylene and oxygen, with the abovementioned dimensions of cross-section of fluidized layers, are in the ratio 6.3: 1.

The reaction gas withdrawn through a vacuum pump is partly liquefied by strong cooling or compression. The amount of uncondensed gas is ascertained by mean of a measuring apparatus.

As soon as a temperature of 615 to 620 C. has been reached, the electric heating is shut ott because the reac- C; hydrocarbons prior -to the dehydrogenation 94.2 Total C hydrocarbons after the dehydrogenation 88.8

The butadiene yield in this experiment accordingly amounts to Diiference 9% of the butylene is continually reacted to carbon during the dehydrogenation, and this carbon is burnt.

The same results are obtained when the experiments are carried out in the arrangement of apparatus illustrated in FIGURE 3.

(b) If the same experiments as are described in Example 1(a) are carried out in the same reactor but without the inner insertion, by introducing the oxygen through the perforated base and the butylene through a gas inlet pipe opening into the fluidized layer, then with the same throughput as in Example 1(a) the catalyst after two hours is laden with 6.4% and after 20 hours with 36.8% of carbon as a result of which the activity falls considerably. The yield of butadiene after 2 hours is only 40% with reference to reacted butylene and after 20 hours has fallen to 29% with simultaneous worsening of the degree of conversion from 17% to 10%.

Example 2 (a) A butane mixture which consists of 67% of butane with a content of C hydrocarbons of 1% and 31% of butenes with a content of C hydrocarbons of 1%, is dehydrogenated at 615 C. in the experimental apparatus described in Example l-(a) under a pressure of 100 mm. Hg-in a fluidized catalyst consisting of A1 with-12% of Cr O of which the amount corresponds to 350 ccs.

The hourly throughput amounts to 30 liters of the butane-butene mixture and 5 liters of oxygen.

The compositions of the reaction products obtained in percent by weight with the deduction of the oxygen of the carbon oxides maybe seen from Table III:

material and in the other zone the material thus pretreatei is subjected to a gasification. A part of the hot car bonaceous residue thereby formed flows back in circu lation into the first-mentioned zone and serves thereii as heat carrier for the pyrolitic distillation. Having re gard to the fact that the reaction mechanism of the sail process is of quite a different kind from the cracking 0 hydrocarbons which is substantially more sensitive o temperature, the possibility of carrying out the proces TABLE III [Composition of the reaction product in percent by weight] Calculated as 0 Butte- Ethane Butyldiene Propane Yield of After hours Hz CH4 ethylene Butane encs degree of propylbutadl- G O C O: converene ene sion (b) If the experiment is carried out under otherwise identical conditions but without subdividing the reactor by an inserted tube, the catalyst is covered with 6.9% of carbon after 2 hours and with 10.2% after 4 hours. The degree of conversion to butadiene is only 6.4 to 8.0%, and the yield 22.7 to 24.5% with reference to reacted C hydrocarbons.

Example 3 (a) In the apparatus describedin Example 1(a), cyclohexane vapor is led at 610 C. under a pressure of 100 mm. Hg through a fluidized layer of aluminum oxide with 12% of chromium oxide. A dehydrogenation product is obtained which consists of 60% of benzene, 1 to 2% of cyclohexene and 37% of unchanged cyclohexane.

(b) By carrying out the dehydrogenation under otherwise identical conditions but without subdividing the re- Example 4 In the apparatus described in Example 1(a) amixtur of 98% pure ethane and 95% pure propane was deh drogenated under a pressure of 50 to '60 mm. Hg in fluidized layer of a catalyst of the grain size 0.1 to 0. mm. consisting of A1 0 with 12% C1 0 the amount the catalyst corresponding to 350 cm The temperature and amounts are specified in Tables IV and V.

TABLE IV [Ethane/ethylene] Throughput 0 Oz 0 O Yield .of (l./h.) calculated calculated H: CH4 CL' t 01H; CaHq ethylene After hours C. as O as 0 (percent) (percent) (percent) (percent) (percent) propylent (percent) (percent) (percent) C2 02 3 50 8 635 5. 25 0. 584 0. 87 0.89 81. 5 10. 0. 52 66 5 8 635 p 4. 4 0. 52 0. 74 0. 76 83. 8 9. 1 0. 67 13 50 5 750 2. 59 2. 4 3. 14 2. 51. 2 35. 8 2. s0 '81. 17 50 5 750 3. 06 2. 32 2. 71 2. 55 51. 4 34. O 4. 07 77,

TABLE V [Propane/propylene] Throughput CO; CO (l./h.) calculated calculated Hz 1 CH 02H G2H4 C3113 03H, 041111 Yield of After hours I C as O as 0 (per- (per- (per- (per- (per- (per- (per- CQHB/C E C 0 (percent) (percent) cent) cent) cent) cent) cent) cent) cent) actor, the catalyst is covered with carbon after a short time. The yield in this case is about 10% less.

US. patent specification No. 2,445,327 describes a fluidized layer process for the simultaneous pyrolitic distillation and exothermic gasi-fication of carbonaceous solids, such as coal, lignite, oil shale, wood and the like in a reactor in the lowerpart of which two reaction zones are so arranged adjacent to each other that they communicate at their upper and lower parts, so that one zone In the two experiments, no carbon deposits are 0 served on the catalyst after 17 and 12 hours, respective] The yields exclude the amounts of oxygen in the o 0 ides of carbon as in Tables II and III.

Example 5 serves for the pyroliti-c distillation of freshly supplied 50 to 60 mm. Hg with an aluminum silicate catalyst.

TABLE VI CO2 CO Naphtha Amount Oalcu- Calcu- H2 CH4 C1115 C2114 Calls 031% C4H1o 04H! CtHt CsHu CsHm After fraction 01 C. oigas lated lated. (Per- (Per- (Per- (Per- (Per- (Per- (Per- (Per- (Per- (Per (Perhours (g.) (l./h.) (l./h.) (aIsC (t cent) cent) cent) cent) cent) cent) cent) cent) cent) cent) cent) erercent) cent) l Residue 53.2% equals 40 g. Residue 47.5% equals 35.5 g.

No carbon deposits on the catalyst can be observed after 4 hours. The residue consists of unreacted naphtha. Formation of aromatic compounds does not occur.

Example 6 In an apparatus according to FIGURE 3, a mixture of methyl butenes is dehydrogenated in the manner described in FIGURE 3 under a pressure of 50 to 60 mm. Hg in a fluidized layer of a catalyst consisting of A1 0 with a content of 15% of Cr O and of K 0.

TABLE VII Moth yl 0; Hz CH4 02H; C 01 CO Isoprene Yield After hours butene (l./h.) 0. (percent) (percent) (+C2I-1 t) (percent) (percent) (perecn t) (percent) percen Example 7 In order to ascertain how far in the bottom fluidized In an apparatus according to FIGURE 3, a mixture of 20% of methyl butene and 80% of isopentane is dehydrogenated in the manner described in Examples 1(a)-6 under a pressure of 50-60 mm. Hg in a fluidized layer of a catalyst consisting of A1 0 with a content of 15% of C1' O and 4% K 0.

layer the oxygen penetrates unconsumed, the suction tube of a paramagnetic oxygen measuring instrument is fixed at different heights in the fluidized layer of a catalyst laden with carbon. Since the measuring instrument does not work at reduced pressure, 14 parts by volume of nitrogen is admixed so that the partial pressure of the oxygen can TABLE VIII Throughput CO1 calc. CO calc. Isopr. cone. Isopr. cone. Methyl After hours hydrocarbons, 0: Temp. Hz CH4 02H; as as C in liquid lnthereactlon butenes Yield g./h. (1./h.) 0.) (percent) (percent) CzI-Ig (percent) (percent) phase at -80 nnxt. (percent) (percent) C. (percent) (percent) No carbon deposits can be observed on the catalyst.

Example 8 In the manner described in Example 2 94% isobutane is dehydrogenated under a pressure of 50 to 60 mm. Hg in a fluidized layer of a catalyst consisting of A1 0 with be kept constant and a gas velocity according to 50 to mm. Hg be set up.

An arrangement of the type used in the experiment is shown diagrammatically in FIGURE 4a of the accompanying drawings. The measurements are given in mm. Through (a) a mixture of oxygen and nitrogen in an a content of 15 of Cr O and 5% of K 0. 6O amount corresponding to a throughput of 4.5 l. 0 and TABLE IX Throughput oi CO2 00 Propane n-Bu- Hz calc. calc. CH Ethane propyltane Iso- Iso- Aiter hours C. (Peras C as 0 (Perethylene ene butylene butane, butyl- Yield,

Hydro- 02 cent) (Por- (Percent) (Per- (Per- (Ierpercent ene, percent carbons (l./h.) cent) cent) cent) cent) cent) percent 6 30 4 650 I 0.98 I 0.96 1 1.71 I 4.03 0- 95 9. 42 I 4.04 i 58.2 20.0 58

No carbon deposits can be observed on the catalyst.

Example 9 The following experiment shows that the dehydrogenatroduce 1. N per hour, and through (b) there is introduced a mixture of 15 l. of butene and l. of nitrogen per hour. For measuring the oxygen content of the gas in- (1 through (a) samples of the gas are taken with 9 the aid of the oxygen measuring instrument (d) at a distance of 10, 20, 30, 40 and 50 cm. from the bottom plate (c).

The results of the experiment are illustrated in FIG- URE 4b. The curves I, II, III, IV and V correspond to the measurements at 10, 20, 30, 40 and 50 cm. from the bottom plate. It can be seen that the oxygen is completely used up by the reaction with the carbon deposits at a height of between 30 and 40 mm. and a reaction temperature of between 450 and 500 C., so that no oxygen can react with the gaseous hydrocarbons.

We claim:

1. In a process for the catalytic cracking of hydrocarbons in a first zone fluidized layer of a catalyst with simultaneous regeneration of said catalyst in a second zone fluidized layer to remove carbon deposits which have accumulated on the catalyst during cracking, the catalyst being in flowing communication and continuous exchange between said firstand second zones, the improvement which comprises: regenerating said catalyst in a vertical columnar regeneration zone of a suflicient height together with the speed of a fluidizing oxygen-containing gas introduced at the bottom of said regeneration zone such that the oxygen is practically completely consumed at the top of said regeneration zone, and introducing hydrocarbon vapors for cracking upwardly in a separate vertical columnar cracking zone located at least partly above said regeneration zone such that the fluidized catalyst is in flowing communication and continuous exchange between said two zones only at the top of said regeneration zone, said two zones forming together a single dense phase fluidized layer of catalyst with a single top surface, the top of said regenerationzone being at a suflicient distance below said top surface of the fluidized layer for exchange of catalyst particles between said two zones.

2. An improved process as claimed in claim 1 wherein the regeneration zone is arranged substantially concentrically within the cracking zone and is separated from said 7 cracking zone by a vertical wall and wherein the communication between the two zones takes place only at the upper end of said zones above said vertical wall.

3. An improved process as claimed in claim 1 wherein there are a plurality of regeneration zones arranged in alternating concentric annular relationship with at least one cracking zone by a plurality of vertical walls and wherein communication between cracking and regeneration zones takes place only at the upper end of said zones above said vertical walls.

4. An improved process as claimed in claim 1 wherein the cracking zone is arranged entirely above the regeneration zone, the oxygen-containing gas being supplied at the bottom of the regeneration zone and the hydrocarbon vapors being supplied to the cracking zone at a point corresponding to the bottom of said cracking zone and located adjacent to and above said regeneration zone.

5. A process as claimed in claim 1 wherein the hydrocarbons to be cracked are n-butenes.

6. A process as claimed in claim 1 wherein the hydrocarbon to be cracked is butane.

7. A process as claimed in claim 1 wherein the hydrocarbon to be cracked is a mixture of butenes and butane.

8. A process as claimed in claim .1 wherein the hydrocarbons to be cracked are methyl butenes.

9. A process as claimed in claim :1 wherein the hydrocarbon to be cracked is a mixture of methyl butane and methyl butenes.

10. A process as claimed in claim 1 wherein the hydrocarbon to be cracked is cyclohexane.

11. A process as claimed in claim 1 wherein the hydrocarbon to be cracked is light naphtha.

.12. A process as claimed in claim 1 wherein the hydrocarbon to be cracked is isobutane.

13. A process as claimed in claim l wherein the hydro carbon to be cracked is ethane.

14. A process as claimed in claim 11 wherein the hydro carbon to be cracked is propane.

1 5. A process as claimed in claim 1 wherein the hydro carbons to be cracked are ethane and propane.

16. A process as claimed in claim 1 wherein the catalys is chromium oxide applied to alumina.

17. A process as claimed in claim 1 wherein the catalys is aluminum silicate.

18. In a process for the catalytic cracking of hydro carbons in a first zone of a fluidized layer of a catalyst witl simultaneous regeneration of said catalyst in a seconr zone of said fluidized layer to remove carbon deposit: which have accumulated on the catalyst during cracking the catalyst being in flowing communication and con tinuous exchange between said first and second zones the improvement which comprises introducing hydrocar 'bon vapors for cracking at the lower end of said crackin;

zone at a 'velocity suflicient to maintain said catalys in fluidized suspension, separately introducing oxygen containing gases at the lower end of said regeneratioi zone at a velocity sufiicient to maintain said catalyst i1 fluidized suspension and at such a rate that the oxyger is practically completely consumed at the top of sair regeneration zone, said fluidized catalyst being in flowin communication and continuous exchange between sail regeneration and cracking zones only at the top of sail regeneration zone.

@19. Apparatus for the catalytic cracking of hydrocar bons and simultaneous regeneration of the catalyst 1] remove carbon deposits which have accumulated on th catalyst during cracking, said cracking and said regenera tion being carried out in a single vertical reaction cham her, which apparatus comprises: an enclosed vertica reaction chamber; a perforated base plate across the bot tom of said chamber; vertical divider means including a least one vertically elongated tubular wall extending up wardly from said base plate within said chamber to sep arate said chamber into at least one regeneration zone an at least one cracking zone, said reaction chamber being 0 sufiicient height to provide a common gas space abov said divider means for exchange of catalyst between sai cracking and said regeneration zones; means to corr pletely block the flow and exchange of catalyst betwee said zones at and below said base plate; at least one ink means to supply a hydrocarbon into the cracking zone c said reaction chamber; at least one inlet means to suppl an oxygen-containing gas into the bottom of the regenerz tion zone of said reaction chamber; and at least one on let means to remove gas passing upwardly from sai cracking and regeneration zones.

20. Apparatus for the catalytic cracking of hydrocar bons and simultaneous regeneration of the catalyst t remove carbon deposits which have accumulated o the catalyst during cracking, said cracking and said reger eration being carried out in a single vertical reactio chamber, which apparatus comprises: a tubular reactio chamber having substantially vertical side walls, a to and a bottom enclosing a single open reaction space; perforated base plate across the lower end of the reactio chamber; means to introduce a fluidizing and oxyger containing gas at the bottom of said reaction chamber an through said base plate over substantially the entire cros section of said reaction space; a hydrocarbon distributr plate arranged at a variable distance above said base pla' at a point corresponding to the top of a lower regener: tion zone in said reaction space where oxygen is practical completely consumed, said distributor plate having smaller cross-section than that of the reaction space; ll let means to supply a hydrocarbon to said distributr 1 i 1 2 plate; and outlet means at the upper end of said reaction 2,378,342 Voorhees et a1. June 12, 1945 chamber for removal of the reaction gas. 2,422,501 Roetheli June 17, 1947 2,875,150 Schuman Feb. 24, 1959 References Clted 111 the file 0f 'EhlS Pate 2 5 343 w b k May 5 1 59 UNITED STATES PATENTS 5 2,899,376 Krebs et a1 Aug. 1 1, 1959 2,249,337 Visser et a1 July 15, 1941 

1. IN A PROCESS FOR THE CATALYTIC CRACKING OF HYDROCARBONS IN A FIRST ZONE FLUIDIZED LAYER OF A CATALYST WITH SIMULTANEOUS REGENERATION OF SAID CATALYST IN A SECOND ZONE FLUIDIZED LAYER TO REMOVE CARBON DEPOSITS WHICH HAVE ACCUMULATED ON THE CATALYST DURING CRACKING, THE CATALYST BEING IN FLOWING COMMUNICATION AND CONTINUOUS EXCHANGE BETWEEN SAID FIRST AND SECOND ZONES, THE IMPROVEMENT WHICH COMPRISES: REGENERATING SAID CATALYST IN A VERTICAL COLUMNAR REGENERATION ZONE OF A SUFFICIENT HEIGHT TOGETHER WITH THE SPEED OF A FLUIDIZING OXYGEN-CONTAINING GAS INTRODUCED AT THE BOTTOM OF SAID REGENERATION ZONE SUCH THAT THE OXYGEN IS PRACTICALLY COMPLETELY CONSUMED AT THE TOP OF SAID REGENERATION ZONE, AND INTRODUCING HYDROCARBON VAPORS FOR CRACKING UPWARDLY IN A SEPARATE VERTICAL COLUMNAR CRACKING ZONE LOCATED AT LEAST PARTLY ABOVE ABOVE SAID REGENERATION ZONE SUCH THAT THE FLUIDIZED CATALYST IS IN FLOWING COMMUNICATION AND CONTINUOUS EXCHANGE BETWEEN SAID TWO ZONES ONLY AT THE TOP OF SAID REGENERATION ZONE, SAID TWO ZONES FORMING TOGETHER A SINGLE DENSE PHASE FLUIDIZED LAYER OF CATALYST WITH A SINGLE TOP SURFACE, THE TOP OF SAID REGENERATION ZONE BEING AT A SUFFICIENT DISTANCE BELOW SAID TOP SURFACE OF THE FLUIDIZED LAYER FOR EXCHANGE OF CATALYST PARTICLES BETWEEN SAID TWO ZONES. 